about how much clearance is there needed between the downpipes and the floorboard in order for the pipes to not hit the floor? i have the mac mids with the catted y-pipe. i can just fit a finger in between the cat and the floor..... seems like when i step on the gas right off idle it will briefly hit/vibrate for a second or two and thats it. doesnt hit at speed or anything.

 

I would leave the exhaust positioned right where you have it and install a set of Poly Motor Mounts. I'll be that would eliminate any movement thats allowing the cat to briefly touch the floorpan.

 

+1 with Mumbles. The finger width plus poly motor mounts should be plenty.

 

how hard is it to install poly motor mounts? is it something i can do in a couple hours in my driveway or is it more of a job for a shop with a lift? this car is also almost a daily driver so will the poly mounts make the car vibrate more or no?

 

Look up the poly install write up. It is NOT an easy job and will take a weekend to do.

 

o great lol. im not gonna be bothered installing poly mounts. any way id spend a whole weekend under this car is if i was gonna be picking up 20-30hp at least. if i cant get this thing to line up ill just pick up the off road version of the mac y-pipe and put that on there and see if that cures the rattle problem. if it doesnt than maybe the headers are hitting somewhere. it was a hell of a tight fit getting them in there so i wouldnt be surprised. there is one screw that looks like it attaches to one of the heat shields on the driver side that is sticking out practically touching the headers so MAYBE when the engine is running it will sometimes hit.

 

If you add 20-30hp, your Y-pipe is gonna bang the floorpan instead of just kissing it, as may be the case now, with the stock motor mounts.

Don't be afraid of the polys. I've done three sets on three different cars. I haven't noticed any new vibrations in any of them. And as for the difficulty of the installation, yeah it can be a bitch. But I believe when I was researching for my first time, I read somewhere, if you can complete a poly motor mount install on a 4th Gen F-body, you have no reason to be afraid of performing any other upgrade to your vehicle. Like I said, I've now done three. If I can do it, you can do it. You'll be glad you did when you're done. Good luck.

 

i get wat ur sayin bout more power will make the y-pipe hit harder..... thing is though its not hitting under full throttle or if it is it cant be felt. its only under light throttle right off idle from like 0mph to 5mph and thats it so i can have 1 million hp and it wouldnt make a difference lol.

 

Keep in mind the pipe bumping is going to set off your knock sensor which will retard your timing and hurt your performance as long as it is doing so.

 

Not sure I quite follow you here, but thats no problem. If you can live with what your car is doing right now, than by all means go with it.

I hope I'm not coming off as trying to tell you what you have to do to your car. If I am, I'm sorry for that. My car, is my car, and no one is gonna tell me what I have to do to it. So please don't let me get away with doing that to you. Polys will fix this problem though, as well as preventing the possibility of others. For example:

Give it some thought, then decide whats best. Good luck.

 

thanks

 

finally got a chance to get back under the car yesterday to see if there was anything i could adjust so that the pipes wouldnt hit the floor and i found something. i found the end of a bolt that was sticking out and hitting one of the primaries on the driver side headers. the bolt had a nut on it holding one of the heat shields on and there was about 1/4 inch of bolt sticking out past the nut so i got in there with a really long skinny saw and was cutting for over a half hour but got through it and now theres no more vibrating. just glad that was all it was so that i wont have to go through the hassle of the motor mounts and stuff. there should be a write-up on this for people with mac headers so that they can grind that bolt down before installing the headers to save lots of time and headaches later.

 

Thats great, man! The simpliest solution, is usually the best solution. Good job, dude.